You can't send warm-blooded animals through the United States Postal Service.
I was on the USPS.com website, trying to find out if I could use a liquor packing box as a shipping container, if it doesn't contain liquor (you can, but you have to mark out any references to beer, alcohol, or related pictures; and you can't wrap the box to do it).
And I stumbled across their "Frequently Asked Questions."
"Are warm-blooded animals mailable?"
The answer was pretty straightforward:
"Warm-blooded animals such as a cats, gerbils, hamsters, mice, dogs, etc are not mailable through the Post Office. Some exceptions exist, for further information contact your local Post Office."
What bothers me is most laws, rules, guidelines, and FAQs come into being come about because somebody tried something they shouldn't have.
Somebody tried this?
And look at the specificity of the response. Gerbils? What, was Richard Gere using Postal Mail? (Right, that's not fair.)